drm/i915: fix invalid reference handling of the default ctx obj
drm/i915: fix invalid reference handling of the default ctx obj

Otherwise we end up trying to unpin a freed object and BUG.

Signed-off-by: Chris Wilson <711c73f64afdce07b7e38039a96d2224209e9a6c@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <73675debcd8a436be48ec22211dcf44fe0df0a64@bwidawsk.net>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs